The preparation of hydrocarbons from a mixture comprising carbon monoxide and hydrogen, by contacting this mixture at elevated temperatures and pressure with a suitable catalyst, is known in the literature as the Fischer-Tropsch process. Suitable catalysts for this synthesis reaction are amongst others catalysts comprising cobalt supported on a porous, inert carrier. Optionally a noble metal, e.g. ruthenium, may be added. Furthermore, the catalysts preferably contain at least one other metal from Group IVb and/or VIb, most preferably chosen from the group consisting of hafnium, zirconium, titanium and chromium. Magnesium, thorium and manganese may also be used. The catalysts preferably contain about 3-80 parts by wt cobalt, especially 15-50 parts by weight of cobalt, optionally 0.05-0.5 parts by wt ruthenium, and about 0.1-100 parts by wt of other metal (as per 100 parts by wt carrier), preferably 5-40 parts of zirconium. The porous carrier is preferably a refractory oxide carrier, such as silica, alumina, zirconia, titania and mixtures thereof; preferably silica is used. Impregnation and/or kneading are conventional methods for the incorporation of cobalt and optionally the promotor and other metals into the carrier. For further information reference is made to EP-A-127,220.
The metal loaded carrier is dried in order to remove the solvent at temperatures varying from ambient temperature to 200.degree. C. at normal pressure. Thereafter the dried catalyst composition is calcined at temperatures from 200.degree.-700.degree. C., preferably 300.degree.-600.degree. C., in order to remove crystal water and to decompose organic and inorganic compounds to oxides and volatile decomposition products, for instance nitrogen oxide.
The catalysts are preferably used in the form of spherical, cylindrical or lobed particles having a nominal diameter of 0.5-5 mm, preferably 1-2 mm. The carrier particles may be prepared by any conventional method, such as compression, granulation, (hot)pressing or extrusion of powderous carrier material, optionally using a binder material. Carrier spheres, in particular silica containing spheres, are suitably prepared by means of the "oil-drop" method, wherein spheres are formed from drops of silica precursor and an acid solidifying when falling in an oil bath, or by means of the "sol-gel" method. Alumina based carriers are preferably made by extrusion or by the above described "oil-drop" method.
Prior to the use of the above-described Fischer-Tropsch catalysts, the catalysts have to be activated. This activation is suitably carried out by contacting the catalyst at a temperature between 100.degree. and 600.degree. C., preferably between 200.degree. and 350.degree. C., with hydrogen or a hydrogen containing gas.